The big bands were mostly made of men and in the swing era, men swung the rhythm while the role of women was usually confined to singing. And then there were exceptions. Mary Lou Williams was the most prominent female jazz pianist of those times and is usually mentioned in histories of swing jazz and also for her role as mentor to bebop. However, a fuller account of her accomplishments went unreported until Tammy L. Kernodle’s biography, Soul on Soul. The new edition considers Williams’ legacy, especially in the field of religious music (her mass is increasingly performed) and as a focus of scholarship on the accomplishments of Black women in music.